I have labored long and hard trying to help people block annoying robocallers and scammers only to be told this or that is meaningless or doesn’t work.

People tell me the Do Not Call Registry is useless and that filing complaints with the registry doesn’t accomplish much.

The Federal Trade Commission disputes that, of course.

My latest advice is to use “selective call rejection” and “anonymous call rejection” offered by both Cox Communications and CenturyLink, for a charge, of course.

Somehow both sound like a way to dismiss rejected suitors.

“Selective call rejection” allows you to program your home phone to reject calls from numbers you place on the list. The other rejects all anonymous calls.

After you pay to not play, a caller on the list, such as an ex-spouse or a persistent robocaller, or any anonymous callers, will hear that you are not accepting calls at this time.

Unblocked calls ring through as usual.

I’m not going to provide the step-by-step procedure to use either anonymous-call rejection or selective-call rejection. Those are available from your phone company.

The kind-hearted woman who shared her experience said the option to block certain callers immediately after they call hasn’t stopped all the annoying calls, but has stopped a great many.

“I hope you can spread the word to your fellow readers and hopefully we can all enjoy it when the phone rings, and it is really someone we want to speak with,” she wrote.

As I was preparing to share this helpful tip, a friend of mine who didn’t want to be identified shared his thoughts.

Politicians need to learn that passing a law does not solve a problem unless the law is enforced, he opined.

This retired federal investigator was pestered by a carpet cleaning company calling three or four times a week.

He did what former investigators do, he investigated, found the name of the company and ratted them out to the Federal Trade Commission, as I recommended in Saturday’s column.

After nothing happened, he called the FTC, only to be told that since Nevada has a Do Not Call law, he had to go to state authorities. He went to the attorney general’s office, then to consumer affairs, to no avail.

Then he found out the company didn’t have a business license, so he went to the Clark County Business License Department. They wanted him to put it in writing and would not say if the company had prior complaints.

“I put together an investigation worthy of a federal agent and sent it to business licensing,” he wrote in an email.

Eventually, he was told there was nothing business licensing could do.

He contacted his phone company to add “select call rejection” to his features, and the carpet cleaning company became the first number he blocked.

Problem solved, right?

Nope. Now he’s telling me there is a limit to how many calls he can block and devil telemarketers have learned to use a large variety of numbers.

He has succeeded in blocking the nice little old lady in a nursing home who calls him by accident because his number is one digit off her daughter’s.

The simplest way, I’m told by many, is simply to screen your calls with an answering machine. After one or two unanswered rings, the robocalls and scammers apparently give up.

Meanwhile, the FTC isn’t giving up. It held a contest asking the technologically advanced to figure out the best technical solution to block illegal robocalls on land lines and mobile phones. The winner gets $50,000.The contest has been whittled down to three entries.

Please, please, please let them figure out a way to stop this madness.